High strength wrinkle resistant cotton fabrics produced by a process involving both monosubstitution and crosslinking of the cotton

ABSTRACT

Improvement in the wear resistance of cotton fabrics in socalled wash-wear or durable press garments is attained using a concept of treatment referred to as SSX involving swelling conducted to increase sites for chemical reactions, substitution to introduce bulky, plasticizing side groups and crosslinking the distended polymer network in cotton fibers to achieve more uniformly placed crosslinks than in prior known wrinkle resistance treatments.

I United States Paton 1151 3,656,85 Gagliardi [4 Ar. 1, W72

[54] HIGH STRENGTH WRINKLE 3,369,857 2/1968 RESISTANT COTTON FABRICS 3,427,121 2/1969 PRODUCED BY A PROCESS 3,434,794 3/1969 INVOLVING BOTH 3,451,763 6/ 1969 3,486,838 12 1969 MONOSUBSTITUTION AND CROSSLINKING OF THE COTTON OTHER PUBLICATIONS [72] I v n n i k D ld G Ii -di, E G Munzel et al. Textile Research Journal, Vol. 36, pp. 230- 238 8 l' d' 1 T '1 R 111 1v137 118 t t .[73] Assignee: Cotton, Incorporated, Memphis, Tenn. 3 a ex 1 e esearc ouma 9 pp [22] Filed: Nov. 15, 1967 Primary ExammerGeorge F. Lesmes PP 683,135 AssistantExaminer-J. Cannon I A!t0rneyl(emon, Palmer and Estabrook [52] U.S.Cl ..8/1l6.3,8/1l5.5,8/ll5.6,

8/1l5.7, 8/116, 8/120, 8/129, 8/17, 8/18, 8/127.6, ABSTRACT 8/DIG' S/DIG' S/DIG' g" Improvement in the wear resistance of cotton fabrics in so- '23 g 3 2? 62' 9% called wash-wear or durable press garments is attained using a 2; 'L' 13/ O g 3 1 2 7, concept of treatment referred to as SSX involving swelling 1 [e 0 3 4 fi conducted to increase sites for chemical reactions, substitu tion to introduce bulky, plasticizing side groups and crosslink- 56 R f Cited ing the distended polymer network in cotton fibers to achieve 1 e erences more uniformly placed crosslinks than in prior known wrinkle UNITED STATES PATENTS resistance treatments.

3,246,946 4/1966 G d ..8/1 16.3 10 Claims, No Drawings BACKGROUND OF THE INVENTION For many years it has been generally recognized that crosslinking of cellulosic fibers causes reduction in tensile strength, tear strength and abrasion resistance of the treated fabrics. In the first generation of wrinkle resistant .cotton fabrics, only minor modification of the fibers was effected to yield wrinkle recovery values (W+ F) of about 200 230 in the fabric. In the second generation of washand-wear fabrics, the modification or crosslinking was increased to produce wrinkle recovery angles of about 240 260. Now some concern was felt about the reduced tensile strength, tear strength and abrasion resistance of the fabrics. To alleviate the problem, fabrics with stronger and heavier yarns were constructed, mercerization was increased, and softeners or thermoplastic resinswere 2 added to the treating bath. In the third and present generation of durable press fabrics, which demand 270 300 wrinkle recovery values and high smoothness and crease retention ratings, the crosslinking agent concentration has had to be greatly increased. This increase now presents a very serious problem in the wear life of cotton durable press gan'nents and has been of great concern both to the cotton industry and to the man-made fibers industry which needs cotton to produce many suitable fabric blends.

Many investigators have been at work to try to find a practical solution to producing high strength cotton in durable press fabrics. Some of the developments which have had varying degrees of success and are beginning to be commercially exploited include: Differential Crosslinking of Cotton Fabrics (l) (2); Vapor Phase Permanent Press (3) (4); Vapor Phase Grafting and Permanent Press (5) (6); crosslinking cotton in the presence of a non-reactive, non-volatile cellulodilator (7) (8); use of high loadings of thermoplastic polymers (9); two

stage crosslinking (10); wet fixing (ll); polymer loading and crosslinking (12) and fabrics from crosslinked and uncrosslinked fibers (13). In some of these prior operations, fiber reactive compositions having inherent fiber swelling properties have been used in crease-proofing treatments, but these have not been utilized to produce higher strength fabrics because they have always been used in non-swelling concentration ranges.

In spite of the extensive investigation and other work mentioned above, there is still a need for other methods and techniques to achieve more profound improvements in all properties of durable press cottons under simplified plant treating conditions.

OBJECTS A principal object of this invention is the provision of a new concept for attaining improvements in thewear resistance of cellulosic fabrics treated toimpart wrinkle resistance characteristics, so-called wash-wear or durable press treatments.

Further objects include the provision of:

1. Substantial improvements in all properties of creaseproof treated cotton fabrics;

2. Such improvements which may be attained .under 'simplified treating conditions;

3. Information concerning the SSX concept for creating high strength cotton through swelling, substitution and crosslinking;

4. Major improvements in the tensile strength, elongation, tear strength, toughness, flexing resistance, and surface abrasion resistance of wrinkle resistant cotton fabrics;

5. Information on the swelling effect of various organic structures and on the synthesis of cellulose reactive. monofunctional and polyfunctional swelling analogs.

Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter; it should be understood, how- .unat

ever, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

SUMMARY OF THE lNVENTlON The wear resistance of a cotton fabric is a complex phenomenon which depends on fabric weight, fabric geometry, yarn structure and size, and fiber properties. Secondarily it depends on the absence or presence of lubricating or sizing finishing agents. It is known that cotton is made up of long-chain cellulose molecules and that these are held together by strong hydrogen bonds in certain crystalline regions. There are other regions, however, having less or no crystallinity. These contribute to fiber elongation and flexibility. The combination of long-chain length, hydrogen bonding 0 and flexibility contribute to the normal high toughness of cotton. When chain slippage occurs, as in forming a wrinkle, this structure, however, is not capable of recovering to its initial state and permanent deformation occurs. It has now been established asa result of the present invention that in the normal process of treating cotton with crosslinking agents, only about 10-l5 percent of the cellulose structure is accessible to the reagent. This limited accessibility results in crosslinkages being concentrated in the flexible, accessible regions. While this concentration of crosslinkages is desirable for preventing chain slippage and producing wrinkle resistance, it is, on the other hand, undesirable for maintaining toughness. Now the original flexible joint has become rigid, brittle and subject to localized stress accumulation. Under stress, this brittle joint can no longer distribute the applied load among all the structural elements and lower tensile, elongation and toughness results so there is a reduction of both elongation and tensile strength. The magnitude of these changes is highest for linen, medium for cotton and least for rayon. The overall results of this lowering of fiber elongation and tensile strength are reflected in a lowering of the area under a stress-strain curve drawn for any cellulosic fiber. This area relates directly to the work (W) required to rupture a fiber and can be approximated by the empirical equation for toughness (L X E )/2. Resistance of a fabric to abrasion (A) is related to the work (W) to rupture fibers and to the toughness value l5 It has now been found that mitigation of the loss of abrasion resistance in crosslinked cellulosic fibers can be attained by not reducing thefiber toughness though eliminating the formation of localized, brittle joints formed in prior known crosslinking treatments.

Broadly stated, the new methods of treating cellulosic fabrics involves: (a) swelling the cotton fibers, (b) introducing bulky, plasticizing side groups and (c) crosslinking the distended polymer structure. By eliminating or minimizing the sharp distinction between crystalline and amorphous, or more accessible, regions there results a more even distribution of crosslinkages through the polymer network. Secondly, the presence of bulky side groups provides for an internal plasticizing effect and further minimizes localized stress accumulation in the fibers.

Advantageously, attainment of high strength, creaseproofed cellulosic fabrics according to the present invention comprises:

a. swelling the fibers of the fabric in a medium capable of swelling cellulose to a greater extent than water;

b. conducting a monofunctional substitution of cellulose molecules in the fibers when so swollen and,

c. crosslinking the substituted and swollen fibers.

Success of this invention is, in part, due to the discovery that cotton fabric properties are greatly dependent on the highly crystalline hydrogen bonded regions and on the flexible, socalled amorphous regions and that the rigid, brittle, joint introduced by wrinkle proofing agents may be plasticized by the dissolution of hydrogen bonds in the crystalline regions by the presence of a highly polar compound, e.g., urea. This leads to a more flexible structure and to restoration of tensile strength. This SSX invention concept further involves the discovery that if one eliminates or minimizes the wide differences between crystalline and amorphous regions in resin treating or crosslinking of cotton to obtain improved wrinkle resistance, then critical improvements in ultimate strength properties of the treated fabric may be obtained.

EXAMPLES The SSX technique as referred to herein may be accomplished in a number of sequential reactions which involve separate steps of swelling, substitution and crosslinking. Advantageously, from a commercial viewpoint, the SSX method may be accomplished in a version of lesser number of steps by the use of certain classes of reagents. Preferably, one uses pairs of highly polar, cellulose swelling, monofunctional and polyfunctional cellulose reactive organic compounds and performs a precure or delayed cure durable press process in a single step.

The following details of operations in accordance with the invention and reported data illustrate the further principles and practice of the invention to those skilled in the art. In these examples and throughout the remaining specification and claims, all parts and percentages are by weight unless otherwise specified.

EXAMPLE 1 This example concerns pairs of monofunctional and polyfunctional reactive swelling agents for cotton.

In one case of evaluation of pairs of reagents, swelling measurements were made on different relative mixtures of monomethylol and dimethylol forrnamides and acetamides. All mixtures gave swelling indices greater than 2.0. The acetamide series, however, all caused greater cotton swelling than the formamide pairs.

As a separate operation, pairs of N-methylol polar compounds were prepared in aqueous solutions under alkaline conditions and, then, when reaction was completed, the solutions were neutralized with hydrochloric acid to pH 7.0-7.5.

These solutions were then used to treat 7 oz. kier boiled and bleached cotton twill fabric. The fabrics were padded through the solutions of reactant pairs at 70-80 percent wet pickup, frame dried minutes at 250 F., cured 10 minutes at 320 F., scoured, refrained and dried in air at 70 F.

In yet another operation, cufi wear tests were made with the twill fabric which was padded and dried 5 minutes at 220 F. Then it was made into trouser cuffs, hot-head pressed and then finally cured 10 minutes at 320 F. Wear tests were made in an automatic washing machine using a built synthetic detergent.

One series of pairs of polar compounds tested as noted above involved monomethylol acetamide (MMA) as one component at concentrations of 5, 10, and 30 percent and one of the following polyfunctional reagents at 10 percent concentration:

dimethylol ethylene urea (DMEU) dimethylol dihydroxy ethylene urea (DMDHEU) polymethylol methoxyethyl carbamate (PMMC) methylated urea-formaldehyde resin (MUFR) Also, fabric was treated with aqueous solutions containing 10 percent of these polyfunctional reagents without the MMA. The crease resistance properties of the treated fabrics (M- CRA, W+F) are reported in the following table:

PMMC

MUFR

EXAMPLE 2 This example concerns fabric treatments with DMEU-M- MA combinations.

The general procedures of Example 1 were repeated using a series of solutions containing 10 percent of DMEU and varying proportions of N-methylol acetamide. The results of the tests on the resulting fabrics are reported in the following table:

TABLE XI N0. washes 1st hole Tensile W-lbs.

Crease bath reten.

The data of the table show that wrinkle resistance is not substantially changed by the addition of the MMA. However, the tensile strength is materially increased as are Stoll Flex abrasion and practical wear resistance. With no MMA, the first hole formed in four washes and after five washes there were also four total failures in the trouser cuffs. As the amount of MMA in the solutions increased, the number of washes to form a hole greatly increased. Also the total number of failures after five washes decreased (Failure equals one thread broken or one hole).

The table demonstrates the value of the concept of using a combination of monofunctional and difunctional cellulose reactive swelling agent in durable press cellulose fiber fabric treatments to obtain better overall strength.

EXAMPLE 3 A series of fabric treatments was performed repeating the general procedures of Example 1 with solutions containing 10 percent DMDHEU and varying concentrations of MMA. The results of the standard tests for wrinkle resistance, strength, etc., performed on the resulting fabrics are reported in the following table:

TABLE XII MC RA Percent (W+F) No. No. NMA in Tensile Stoll Crease washes failures W'lbs flex reten. 15!; hole 5 washes The table data show a slight drop in wrinkleproofing performance at higher concentrations of MMA with, however, a substantial improvement in all strength and wear properties.

EXAMPLE 4 Practical delayed cure cuff wear tests were performed using the general procedures of Example 1 to treat fabric with two separate solutions, one containing 10 percent DMEU without MMA and the other containing 10 percent DMEU and 10 percent MMA (plus in both cases the standard 1 percent zinc nitrate catalyst). The test results are reported in the following table:

The reported data show the mixed pair of reagents produced about three times the wear life of the control durable press treatment.

EXAMPLE 5 The procedure of Example 4 was repeated using DMDHEU in place of DMEU. The results are reported in the following table:

TABLE XIV Percent Percent No. of Total No. DMDHEU N-methylol washes for of f ilures in bath acetamide Cuff No. 1st hole washes None A 4,4 13,12

No e B 3,3 11,13

None 0 3,3 13, 14

None D 3,4 18,18

1 Percent MMA.

The reported data show dramatic increase in wear performance of durable press treatments using dimethylol dihydroxyethylene urea with N-methylol acetamide as compared to the DMDHEU alone.

EXAMPLE 6 This example concerns the use of N-methylol pyrrolidone (NMP),i.e.,

CHzC=O N-CHZOH CH -CH2 and N-methylol acetamide )MMA), i.e.,

l? CHa-C-NH CHQOH TABLE XV Percent Stoll Wear Finishing N -methy1o1 MCRA Tough- Tear flex test. llliX compound (W+F) ness W W W Untrcated... Untreated. 149 793 1, 536 613 1, 435 D1 (:o|1tr0l None.- 294 281 1,056 166 299 10% DMEU 10% MMA-.- 298 387 1,536 932 1, 807 300 352 1, 568 710 8, 310

10% DMEU 10% NMP EXAMPLE 7 This example concerns a delayed cure finish on cotton fabric using a combination of dimethylol oxamide (DMO) and monomethylol acetamide (MMA) as the monoand di-functional pair of treating reagents. Fabric sections were treated with four separate solutions containing varying proportions of the tworeagents. Test results performed on the fabrics treated with these solutions using the general procedure of Example 1 are reported in the following table:

TABLE XVI Percent Percent MO RA Toughness Tear Stoll dimethylol N-methylol flex oxamlde acetamide F W W F W F W Untreated. Untreated 92 99 730 421 1, 600 1,088 832 16 0 143 121 284 1,504 800 502 16 10 145 128 314 143 1, 792 1,088 2, 136 20 20 144 125 510 176 1, 824 1, 216 2, 278

The reported data show a critical improvement in strength and wear properties is obtained by the combination of the monofunctional reagent with the difunctional reagent.

EXAMPLE 8 This example concerns use of the combination of dimethylol succinamide as the difunctional creaseproofing agent and N-methylol acetamide as the monofunctional reagent. The investigation also included a durable press control run using a standard DMEU treatment solution for comparison purposes. The general procedure of Example 1 used to treat and test the fabric resulted in the data reported in the followingtable:

TABLE XVII The usefulness of dimethylol succinamide as a creaseproofing agent is limited because of limited water solubility of the compound and the lack of chlorine resistance in the treated fabric.

TEST VALUES The physical tests employed to evaluate the effects produced in the treated fabrics in the above examples are as follows:

MCRA Monsanto Crease Recovery Angle in degrees total warp plus filling unless specified otherwise. Fed. Spec. CCC-T-l9 1b., Method 5212.

'Note: Wet MCRA values are obtained by soaking the test specimen in distilled water with 0.1 percent wetting agent at room temperature for 1 hour, blotting with blotting paper and testing as above.

Tensile Strength Grab Method in CCC-T-l 9 1b., Method 5132.

Flex Abrasion Resistance Cycles to Failure C.S.l. Stoll Flex Tester, 1 lb. tension/1.2 lb. load. ASTM Method Dl l-55T.

Surface abrasion Wyzenbeek surface abrasion test of the American Association of Textile Chemists and Colorists expressed in cycles to failure.

Appearance Procedure for wash-wear items after home laundering, AATCC 88A-l 964T Wrinkle Recovery Wrinkle recovery test method AATCC66-l959T.

DISCUSSION OF DETAILS Treating compositions used in carrying out the SSX crease resistant improving procedures of this invention are aqueous pounds. Fed. Spec.

solutions containing two essential ingredients, namely, (a) water-soluble, heat-curable, polyfunctional nitrogen-containing organic material known to possess creaseproofing properties when used in the treatment of cellulosic fabrics, and (b) a monofunctional organic compound having the ability to react with cellulose to form a substitution product. The invention is preferably conducted using water-soluble amine-aldehyde reaction products known to be useful in the creaseproofing of cotton or other cellulosic fabrics. However, the invention is contemplated for use with any other form of nitrogen-containing, water-soluble organic materials now known to be useful for creaseproofing of cellulosic fabrics or found in the future to be useful for this purpose, e.g., water-soluble alkylated amine-aldehyde reaction products, aziridinyl phosphine oxides or comparable materials.

Specific examples of nitrogen-containing, water-soluble, heat-curable organic cellulose fabric creaseproofing materials which may advantageously be used in accordance with the invention include:

From the class of amino-aldehyde reaction products, the monomers and water-soluble polymers of:

dimethylol urea trimethylol melamines dimethylol ethylene urea polymethylol melamine polymethylol alkyl carbamates polyalkylated monoureins (see US. Pat. No. 3,209,010)

N,N-dimethylol or dialkoxymethyl monoheterocyclic ureas represented by the following generic structure:

R-O CH N NCH;OR

where X is: C=0, C=NH, or :8

and R is: H or a lower alkyl and Y is: a divalent alkylene or substituted alkylene radical, as for example:

-CH:CH1, CH;CH;CH7, CH;CO, CH7NCH CHz-OCH2, CHCH, -CR-C R )H OH OR )R CHCH1CH, -CHr-CHCH2- From the class of alkylated amino-aldehyde reaction products, the monomers and water-soluble polymers of:

dimethoxymethyl urea trimethoxymethyl melamine.

From the class of aziridinyl phosphine oxides:

tris aziridinyl phosphine oxide tris methyl aziridinyl phosphine oxide.

In the preferred methods of the invention, the monofunctional reagent is one which has the capability of swelling cellulose to a greater degree than water and advantageously has a swelling index as hereinbefore defined of at least 1.5, especially 1.8 to 2.5. However, the SSX concept also involves the use of a suitable monofunctional, cellulose reactive reagent in combination with a non-reactive cellulodilator to produce the desired swelling of the cellulose. Such swelling with the separate non-reactive cellulodilator may precede the application of the reagents (a) and (b) mentioned above and continue through their application or the swelling may be accomplished simultaneously with the application of the reagents (a) or (b) or (a) with (b).

Various cellulose non-reactive organic and inorganic cellulodilators are known and have been used in various prior processes to dilate cellulose molecules in chemical reactions. This reagent must dilate the cellulosic fibers and keep them dilated during the curing of the creaseproofing agent, even after water has evaporated. It has been found that from this known class of materials, aprotic organic compounds are unique in the new methods of this invention. Dimethyl sulfoxide is the preferred aprotic organic cellulodilator, but other usable organic cellulodilators include dimethyl formamide, dimethyl acetarnide, N-methyl pyrrolidone, 2-pyrrolidone, tetramethyl urea, vinyl pyrrolidone, sodium xylene sulfonate, butyrolactone and dimethyl sulfone.

Lithium thiocyanate is an example of an inorganic cellulodilator. Other inorganic salts higher in the lyotropic series than lithium thiocyanate are also contemplated for use, i.e., water-soluble inorganic salts having greater water of hydration than lithium thiocyanate, e.g., LiBr, CaBr MgCl CaCl zirconium chlorhydroxide and aluminum chlorhydroxide.

Mixtures of aprotic organic cellulodilators with inorganic cellulodilators may advantageously be used. Such mixtures may comprise ratios of organic to inorganic between :1 and 1:100 and preferably between 5:1 and 1:5, especially 4:1 and 1:2.

The treating compositions used to impart wet and dry crease resistance to cellulosic fabrics in accordance with the invention are aqueous solutions containing dissolved therein the nitrogen-containing organic anti-crease agent, the monofunctional organic reagent, a separate cellulodilator if this is used and, preferably, in addition, an acidic aminoplast forming catalyst. Generally, the solutions will contain 1 to 20 percent reactive compound, 0 to 20 percent non-reactive cellulodilator and l to 5 percent of the acidic catalyst.

Specific examples of acidic catalysts which may be used in accelerating the curing of nitrogen-containing compounds and reaction thereof with cellulose in the fabrics include zinc nitrate, zinc chloride, zinc fluoroborate and comparable acid reaction metal salts. In addition, acid reacting salts of ammonia or amines may be used, e.g., ammonium silicofluoride, diammonium acid phosphate, ammonium bisulfate, ethanolamine hydrochloride and the like. Suitable catalysts also include free acids, e.g., hydrochloric, phthalic, tartaric, citric and similar acids.

No special form of equipment is required in carrying out the procedures of the invention. This constitutes an important advantage of the new procedures for it makes possible the easy addition of the operation to established textile finishing and handling plants. Likewise, generally available, commercially used drying, shaping and textile handling equipment may be employed in carrying out the drying, heating and dimension controlling steps of the new operations. Furthermore, the new procedures may be applied in conjunction with other textile processing operations generally considered useful by the textile industry. Such procedures include waterproofing, mildewproofing, calendering, embossing, dyeing, printing and the like. Other known finishing agents not incompatible or detrimental to these new treatments may be applied in conjunction with the creaseproofing agents of this invention, e.g., lubricants, sizing materials, mothproofing agents, waterproofing agents, brighteners, dyes, pigments and the like. Some or all of these types of materials may be included in the actual treating compositions of this invention in amounts advantageously about 1 to 10 percent.

The impregnation of the aqueous treating compositions is probably most easily accomplished by standard padding procedures may be employed, e.g., spraying, brush.application, roller coating, transfer from saturated webs or the like. Whatever procedure is employed, the fabric should be impregnated with sufficient of the aqueous composition so that when the fabric is completely dried, there will remain in the fabric as the non-volatile residue, between about 1 and 20 percent of the nitrogen-containing, creaseproofing agent, and advantageously, 3 to 10 percent by weight of the creaseproofing agent. With the preferred aqueous compositions, this can readily be accomplished by adjusting the impregnation to give a pickup of 50 to 100 percent by weight based upon the dried weight of the fabric or other fiber substrate to which the solution is applied.

Solution composition and fabric pickup is preferably controlled to place in the fabric before the curing step a polyfunctional nitrogen-containing, creaseproofing agent to monofunctional cellulose reactive agent weight ratio of between about 10:1 and 3:20, and a weight ratio of the creaseproofing agent to curing catalyst of between about 100:1 and 1:5.

The aqueous solution impregnated fabrics or other fibrous webs are dried, preparatory to the'heat curing step. This can be accomplished by air drying at room temperature using forced air circulation or, preferably, by heating such as with radiant or convection heat in ovens, tunnels or the like to an elevated temperature between about 50 and 100 C. and especially 100 to 150 C. for between about 1 to 60 minutes. The drying step need not be conducted any longer than necessary to effect substantial complete drying and generally shorter times will be required for higher temperatures.

After the substrate is dried, it is subjected to an elevated heating step in order to effect a curing which appears to involve a condensation of the solid residue materials in the fabric with themselves and with the cellulose. The heat curing is advantageously conducted at a temperature above 100 C. and below the decomposition temperature of the fabric, preferably between 100 and 200 C. and usually for between about 1 to 60 minutes, longer times generally being employed at the lower temperatures and vice versa. Drying and curing can take place at the same temperature if this is above about 100 C. and in the same oven or dryer if desired.

Following the heat curing step, it is advantageous to wash or scour the fabric in order to remove unreacted material. During this stage of the operation, it may be found desirable to treat the fabric with softening agents, sizing agents, lubricants or the like. Following this cleansing, the fabric is dried, preferably using some type of dimension control such as tenters or other dimension control frames or equipment to ensure even drying and squaring of the fabric.

The new creaseproofing operations are particularly useful for the finishing of cotton fabric which will be used for wearing apparel, such as mens shirts, womens dresses, childrens clothing or the like, yard goods, sheeting and similar household fabric. However, the operations are also useful with any other form of fabric including non-woven as well as woven webs, knitted goods and the like composed of fibers of cellulosic origin, e.g., cotton, viscose rayon, acetate rayon, linen and the like. Cloth or other fibrous webs composed partially of fibers of cellulosic origin and partially of other natural or synthetic fibers may also be treated, e.g., webs, containing in part, wool, silk, nylon, acrylic fibers, modacrylic fibers, polyester fibers and the like.

The SSX technique may be done in various ways, for examle: p a. pad, dry, cure immediately;

b. pad, air dry 24 hours, then cure;

c. soak 1 hour, pad, dry, cure.

The cotton or other cellulosic fabric may be sequentially modified by swelling, introducing side groups through alkylation, esterification or grafting, and finally crosslinking it. Such reactions might be done in solvents, in a vapor phase or under aqueous conditions.

As an alternative, one may utilize pairs of monofunctional and polyfunctional cellulose reactive agents which also swell cotton to a much greater degree than water, e.g., to a swelling index of at least 1.8.

Additional swelling agents generally usable in the SSX operations include:

Concentrated zinc chloride solutions Sodium zincate Concentrated sulfuric acid Pyridine Anhydrous ethyl amine Alkaline earth hydroxides Quaternary ammonium bases Cellulose solvents. Formic and acetic acid Cellulose enzymes CONCLUSION New improvements in methods of treating cotton and other cellulosic fabrics to create strong wrinkle-resistant fabrics have been described. Such operations involve introducing bulky side groups and crosslinking the cellulose in a swollen state to eliminate the normally rigid and brittle joints of known crosslinking methods. Such a system produces a crosslinked fiber with greater flexibility and toughness. A series of sequential treatments are reported which have yielded stronger wrinkle-resistant cotton than is given by conventional treating methods.

The embodiments of the invention in which an exclusive property or right is claimed are defined as follows:

1. A process for the creation of wrinkle resistance characteristics in cellulosic fabrics while preserving high strength and wear properties which comprises:

a. swelling a cellulosic fabric by impregnating it in a solution consisting essentially of N-methylol acetamide, a polyfunctional cellulose creaseproofing agent, a catalyst and water;

b. drying; and

c. heat curing the fabric to effect simultaneously both a substitution of the cellulose by reaction with the N-methylol acetamide and a crosslinking of the cellulose with the creaseproofing agent so as to substantially increase the wrinkle recovery of the fabric.

2. A process according to claim 1 wherein the solution in step (a)-contains from 5 to 30 percent N-methylol acetamide by weight.

3. A process according to claim 2 wherein the creaseproofing agent is a polymethylol cyclic urea and is present in the solution in step (a) in a concentration giving a weight ratio of creaseproofing agent to N-methylol acetamide of between about 10:1 and 3:20.

4. A process according to claim 3 wherein the creaseproofing agent is dimethylol dihydroxy ethylene urea.

5. A process for the creation of wrinkle resistance characteristics in cellulosic fabrics while preserving high strength and wear properties which comprises:

a. swelling a cellulosic fabric by impregnating it in an aqueous solution consisting essentially of 5 to 30 percent N- methylol acetamide, 0 to 20 percent non-reactive cellulodilator capable of swelling cellulose to a greater degree than water, and water;

b. reacting the cellulose with the N-methylol acetamide so as to introduce plasticizing side groups into the cellulose while the fabric is swollen;

c. drying the fabric; d. impregnating the fabric with an aqueous solution containing a creaseproofing agent and a catalyst; and

e. drying; and

f. heat curing the fabric.

6. A process according to claim 5 wherein the fabric is a cotton-containing fabric and wherein the creaseproofing agent is a polymethylol urea.

7. A process according to claim 5 wherein the fabric is a cotton-containing fabric and the creaseproofing agent is dimethylol dihydroxy ethylene urea.

8. A durable press treated cellulose fabric containing cellulose substituted by reaction with N-methylol acetamide, prepared by the process of claim 3 and having a wrinkle recovery angle greater than 260 and a tear strength retention of at least 60 percent.

9. A durable press treated fabric according to claim 4 wherein the fabric contains cotton.

10..A composition for the treatment of cellulosic fabrics to impart wrinkle resistance characteristics thereto while preserving high strength and wear properties comprising:

a. N-methylol acetamide, and b. a polymethylol cyclic urea selected from the group consisting of dimethylol ethylene urea and dimethylol dihydroxy ethylene urea, the weight ratio of (a) to-(b) being between 1:10 and 20:3. 

2. A process according to claim 1 wherein the solution in step (a) contains from 5 to 30 percent N-methylol acetamide by weight.
 3. A process according to claim 2 wherein the creaseproofing agent is a polymethylol cyclic urea and is present in the solution in step (a) in a concentration giving a weight ratio of creaseproofing agent to N-methylol acetamide of between about 10: 1 and 3:20.
 4. A process according to claim 3 wherein the creaseproofing agent is dimethylol dihydroxy ethylene urea.
 5. A process for the creation of wrinkle resistance characteristics in cellulosic fabrics while preserving high strength and wear properties which comprises: a. swelling a cellulosic fabric by impregnating it in an aqueous solution consisting essentially of 5 to 30 percent N-methylol acetamide, 0 to 20 percent non-reactive cellulodilator capable of swelling cellulose to a greater degree than water, and water; b. reacting the cellulose with the N-methylol acetamide so as to introduce plasticizing side groups into the cellulose while the fabric is swollen; c. drying the fabric; d. impregnating the fabric with an aqueous solution containing a creaseproofing agent and a catalyst; and e. drying; and f. heat curing the fabric.
 6. A process according to claim 5 wherein the fabric is a cotton-containing fabric and wherein the creaseproofing agent is a polymethylol urea.
 7. A process according to claim 5 wherein the fabric is a cotton-containing fabric and the creaseproofing agent is dimethylol dihydroxy ethylene urea.
 8. A durable press treated cellulose fabric containing cellulose substituted by reaction with N-methylol acetamide, prepared by the process of claim 3 and having a wrinkle recovery angle greater than 260* and a tear strength retention of at least 60 percent.
 9. A durable press treated fabric according to claim 4 wherein the fabric contains cotton.
 10. A composition for the treatment of cellulosic fabrics to impart wrinkle resistance characteristics thereto while preserving high strength and wear properties comprising: a. N-methylol acetamide, and b. a polymethylol cyclic urea selected from the group consisting of dimethylol ethylene urea and dimethylol dihydroxy ethylene urea, the weight ratio of (a) to (b) being between 1:10 and 20:3. 